Sensors are used for a variety of purposes. One useful purpose is as an detection system for detecting the presence of objects. In particular it has been found to be difficult to detect the edge of objects, or objects with small, specular surfaces. A sensor and detection system and method which solves this problem is taught in U.S. Pat. No. 5,504,345, which is owned by assignee, and is herein incorporated by reference. The '345 patent discloses a semiconductor wafer and magnetic disk edge detection system having converging dual-beam optical sensor. The sensor comprises at least two light sources, and at least two light detectors. The light sources, or the light beams emanating form the sources, are spatially oriented such that the focal point of the converging light beams define a focal or inspection plane and converge at a single point external to the sensor. When the object interrupts the beam at or near the focal point of the light sources, it causes the light to be reflected backwards toward the sensor by the light detectors. The light detectors are spatially arranged so they can receive the light reflected.
The '345 patent teaches a very useful device, however it would be useful to increase the angle of coverage of the sensor. When the light strikes the object and is reflected backwards there is a certain angle associated with the return path of the reflected light. It is possible for light to be reflected in a vicinity remote from the light detectors. This results in a "blind spot" where the light is not detected. Thus, it is desirable to provide a sensor and detection system that exhibits improved coverage and substantially eliminates blind spots.